An Arlington woman was sentenced to 48 years in prison yesterday for the first-degree murder of a dry cleaning store proprietor, her former employer, whom she stabbed 54 times in the face, neck, abdomen and back during an apparent robbery attempt.

Arlington Circuit Judge Thomas R. Monroe, in sentencing Patricia J. Mawyer, 18, of the 2000 block of North Madison Street, called the slaying a "very horrible crime," but rejected a request from Commonwealth's Attorney Henry Hudson that she be given a life term. Mawyer will be eligible for parole in 12 years.

"I'm sorry, your honor. I didn't mean it," a sobbing Mawyer said of the knifing on April 14 of 58-year-old Edith Miller, owner of the Old Dominion Dry Cleaning shop, 4036 Lee Hwy. Mawyer, who had worked briefly for Miller last year, pleaded guilty in November.

Hudson, who said in court that Mawyer had threatened to kill him, called the crime "above and beyond being brutal, savage and ruthless. It's almost unparalleled in its malice. After Mrs. Miller had been left dead on the floor, Mawyer continued to stab her 35 times."

Hudson told the court Mawyer's apparent motive was to get money from Miller to bail her boyfriend out of the Fairfax County jail. The state's case was tied to a bloody fingerprint that tests showed Mawyer left on a snack tray in the store.